K & N Filter

This is a discussion on K & N Filter within Technical Stuff, part of the Under the Hood category; Hi guys.
I have heard about K & N Air Filter a lot on team bhp.com,well please excuse my ignorance,but ...

Hi guys.
I have heard about K & N Air Filter a lot on team bhp.com,well please excuse my ignorance,but I don't know what this thing actually is,or what it does,and how it helps the vehicle.
Could someone please advise me whether fitting in this will affect FE,and how much it costs,what are the advantages/disadvantages of fitting in a K & N filter.
Thanks,
Suraj

Even though turbo_lover has given you a great explanation i will suggest you enter "K & N" in the search box and you can go through the numerous threads on the topic.....it has been discussed to the core, some posts are accompanied with pictures to aid understanding........you could also visit the K&N website

Guys,will fitting in a K&N Filter void my company warranty?
Also,is it necessary to tell the service centre people not to tamper with Air Filter during services/repairs,since I have K&N filter?
How long will one K&N air filter work?..like how many years?And approx. cost of performance K&N filter for NHC CVT?